Enhancing the scheduling of a design project can markedly reduce its total duration. However, accurately representing the schedule of a design project is complex, largely owing to that design activities generally depend on information about each other. That is, the design process involves many iterations across activities. Iterative dependency makes difficult defining the logical relationships among activities in the network and evaluating the duration of the project. This work applies a dependency structure matrix to identify design dependencies. Causes and various types of design iterations for a building project are presented. Additionally, an innovative simulation-based model is developed to incorporate the design iterations, deliverables and participants for generating a schedule of a design project. The proposed model can not only assess how design iterations affect the duration, but also evaluate the idle durations of the design participants to support the assignment of design tasks. Effectiveness of the model is demonstrated through its application to an example project.